With the rapid development of electrified railways, the traction load of electrified railways has become the largest single load in China's power system, but the impact of its load characteristics on the small-signal stability of the power system is still unclear. Therefore, an equivalent mathematical model of the traction load of electrified railways is established, and based on this, a small-signal model of the power system considering the access of traction loads is constructed. Secondly, using eigenvalue analysis methods, the impacts of locomotive speed, locomotive quantity, and the access location and proportion of traction loads on the small-signal stability of the power system are analyzed. Finally, the adjustment range of excitation parameters of synchronous generators is determined through eigenvalue root locus, and the impacts of traction loads before and after access and different traction load parameters on the adjustment range of excitation parameters of the power system are analyzed. The research results indicate that after the access of traction loads, the small-signal stability of the power system decreases, the adjustment range of system excitation parameters shrinks, and the system stability margin reduces.